It is very common to have a refrigeration and/or air conditioning requirement and a simultaneous need for hot water. Generally, the refrigeration system is operated totally separate from the hot water system with the result that the heat removed in the condensing process of the refrigeration system is wasted, while the water in the hot water system is heated by means of an external energy source such as gas, electricity, or oil. The cost of such fuel can be great particularly in situations where large amounts of hot water are required. The purpose of this invention is to reduce or eliminate the need for these expensive fuels and to utilize the heat energy in the condensing process of the refrigeration system to produce the hot water.
A primary example of a situation where refrigeration is used and large amounts of hot water are needed is on the modern dairy farm. Such farms have bulk milk coolers into which the milk from the cows is fed by means of automatic milking devices. The milk is fed directly into the central cooler, or bulk milk cooler, during the milking process. These coolers are refrigerated to remove heat from the milk promptly after it is produced. Thus, the evaporator of the refrigeration system is located in the bulk milk cooler with the other components including the condenser unit located elsewhere. Generally, the condenser unit is air cooled in a conventional manner, or it may be water cooled with much or all of the water wasted. In either case, much of the heat taken from the milk as it is cooled is wasted, and it is a primary purpose of this invention to utilize such heat for the production of hot water.
In addition to requiring a refrigeration system for the prompt cooling of the milk, the modern dairy farm also has a large requirement for hot water at different temperatures. For example, on the same farm, large amounts of hot water are needed for prepping the cows, washing the milk cooler, the pipeline, milker, other components of the milking equipment, and the milking parlor itself. It is also desirable to heat the cows's drinking water in the winter. Water at about 100.degree. F. or so would be used for prepping or cleaning the cows, but much hotter water, about 140.degree. F. to 150.degree. F. is required for cleaning the milking apparatus and cooling tank. Of course, if a large quantity of hot water can be produced at 140.degree. F. to 150.degree. F., it follows that larger amounts of warm water, about 100.degree., can easily be available. For example, the appropriate water temperature for prepping cows (approximately 100.degree. F.) can be obtained by either mixing the 150.degree. water discharge through the thermostat with cold water by a commercially available mixing device or by removing water ahead of the thermostat before it reaches 150.degree. and tempering it as required with cooler water. The latter is the preferred method since it materially reduces the condensing temperature, thus increases the refrigerating capacity. Thus, a principal object of this invention is to produce large quantities of hot water by utilizing heat absorbed in the condensing process of the refrigeration system.
Generally, in accordance with this invention, the water is heated by transferring the superheat, heat of condensation and a part of the liquid refrigerant's sensible heat in a uniquely designed heat exchanger. The heated water then circulates by convection, when the water reaches a selected temperature, into a hot water storage tank where the water remains stratified with the hot water at the top of the tank and the colder water at the bottom. As more water is heated in the condensing unit, the marginal line of stratification in the tank moves progressively lower. The tank may fill completely with hot water at the selected temperature.
The heating of water to produce stratification in a hot water storage tank by means of convection is known in the art. One such construction is known as a "sidearm" heater which consists of a hot water storage tank connected between the inlet and outlet of a heater device. The heater device consists of a coil of copper tubing or the like which is located near the bottom and off to the side of the hot water tank. One end of the tubing is connected to the bottom of the tank and the other end to the top. Of course, an inlet is provided at the bottom of the tank from a cold water supply and an outlet is provided at the top of the tank for the dispensing of hot water. A heating element, such as a gas burner, is located just beneath the heater coil to heat the water in the coil by means of outside energy. In operation, the burner heats the water in the coil which causes the water in the coil to rise by convection and enter the top of the storage tank. The water in the storage tank stratifies until the tank becomes completely full of hot water.
It is also known in the art to utilize some of the heat from the condensing process of the refrigeration system to produce hot water in a storage tank. For example, such a system is described in an article in the June, 1962, issue of "Refrigeration Service And Contracting," page 19.
That article describes a system whereby two units are used, one called a "heat exchanger" and the other called a "final condenser" whereby in the production of hot water at approximately 160.degree. F., the superheat is removed from the refrigerant in the heat exchanger, with the remainder of the latent heat and the subcooling heat being removed at the final condenser. The hot water is produced from the heat exchanger only.
In accordance with this invention, hot water at approximately 140.degree. F. to F. F. is produced in a single condensing unit by the removal of the superheat, all the latent heat, and in a preferred embodiment part of the sensible heat from the refrigerant in the single unit.